冬天来了，今早mysql起不来了。
一直在叫嚷着：
Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock'
发火，尝尽各种办法！都不行！为啥咧?!
最后忍无可忍之下，直接卸载了重装，搞定！
原数据也都在，幸好幸好！
以下是重装过程：
sudo apache2ctl stop
sudo apt-get --purge remove mysql-client mysql-server mysql-common
sudo apt-get autoremove
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install mysql-server mysql-client
sudo apt-get install php5-mysql
mysql -uroot -pxxxxxxx
sudo apache2ctl start
===== Log for Mysql at /var/log/mysql/error.log ====
151208 8:08:57 InnoDB: Initializing buffer pool, size = 128.0M
151208 8:08:57 InnoDB: Completed initialization of buffer pool
151208 8:08:57 InnoDB: highest supported file format is Barracuda.
151208 8:09:04 InnoDB: Waiting for the background threads to start
151208 8:09:05 InnoDB: 5.5.46 started; log sequence number 763296054
151208 8:09:05 [Note] Server hostname (bind-address): '127.0.0.1'; port: 3306
151208 8:09:05 [Note] - '127.0.0.1' resolves to '127.0.0.1';
151208 8:09:05 [Note] Server socket created on IP: '127.0.0.1'.
151208 8:09:05 [ERROR] Fatal error: Can't open and lock privilege tables: Table 'mysql.host' doesn't exist
151208 8:09:06 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
151208 8:09:06 [Note] Plugin 'FEDERATED' is disabled.
/usr/sbin/mysqld: Table 'mysql.plugin' doesn't exist
151208 8:09:06 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
151208 8:09:06 InnoDB: The InnoDB memory heap is disabled
151208 8:09:06 InnoDB: Mutexes and rw_locks use GCC atomic builtins
151208 8:09:06 InnoDB: Compressed tables use zlib 1.2.8
151208 8:09:06 InnoDB: Using Linux native AIO
151208 8:09:06 InnoDB: Initializing buffer pool, size = 128.0M
151208 8:09:06 InnoDB: Completed initialization of buffer pool
151208 8:09:06 InnoDB: highest supported file format is Barracuda.
151208 8:09:06 InnoDB: Waiting for the background threads to start
151208 8:09:07 InnoDB: 5.5.46 started; log sequence number 763296054
151208 8:09:07 [Note] Server hostname (bind-address): '127.0.0.1'; port: 3306
151208 8:09:07 [Note] - '127.0.0.1' resolves to '127.0.0.1';
151208 8:09:07 [Note] Server socket created on IP: '127.0.0.1'.
151208 8:09:07 [ERROR] Fatal error: Can't open and lock privilege tables: Table 'mysql.host' doesn't exist
151208 8:09:08 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
151208 8:09:08 [Note] Plugin 'FEDERATED' is disabled.
/usr/sbin/mysqld: Table 'mysql.plugin' doesn't exist
151208 8:09:08 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
151208 8:09:08 InnoDB: The InnoDB memory heap is disabled
151208 8:09:08 InnoDB: Mutexes and rw_locks use GCC atomic builtins
151208 8:09:08 InnoDB: Compressed tables use zlib 1.2.8
151208 8:09:08 InnoDB: Using Linux native AIO
151208 8:09:08 InnoDB: Initializing buffer pool, size = 128.0M
151208 8:09:08 InnoDB: Completed initialization of buffer pool
151208 8:09:08 InnoDB: highest supported file format is Barracuda.
151208 8:09:08 InnoDB: Waiting for the background threads to start
151208 8:09:09 InnoDB: 5.5.46 started; log sequence number 763296054
151208 8:09:09 [Note] Server hostname (bind-address): '127.0.0.1'; port: 3306
151208 8:09:09 [Note] - '127.0.0.1' resolves to '127.0.0.1';
151208 8:09:09 [Note] Server socket created on IP: '127.0.0.1'.
151208 8:09:09 [ERROR] Fatal error: Can't open and lock privilege tables: Table 'mysql.host' doesn't exist
151208 08:13:07 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
151208 8:13:07 [Warning] Using unique option prefix key_buffer instead of key_buffer_size is deprecated and will be removed in a future release. Please use the full name instead.
151208 8:13:07 [Note] /usr/sbin/mysqld (mysqld 5.5.46-0ubuntu0.14.04.2) starting as process 3727 ...
151208 8:13:07 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
151208 8:13:07 [Note] Plugin 'FEDERATED' is disabled.
/usr/sbin/mysqld: Table 'mysql.plugin' doesn't exist
151208 8:13:07 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
151208 8:13:07 InnoDB: The InnoDB memory heap is disabled
151208 8:13:07 InnoDB: Mutexes and rw_locks use GCC atomic builtins
151208 8:13:07 InnoDB: Compressed tables use zlib 1.2.8
151208 8:13:07 InnoDB: Using Linux native AIO
151208 8:13:07 InnoDB: Initializing buffer pool, size = 128.0M
151208 8:13:07 InnoDB: Completed initialization of buffer pool
151208 8:13:07 InnoDB: highest supported file format is Barracuda.
151208 8:13:07 InnoDB: Waiting for the background threads to start
151208 8:13:08 InnoDB: 5.5.46 started; log sequence number 763296054
151208 8:13:08 [Note] Server hostname (bind-address): '127.0.0.1'; port: 3306
151208 8:13:08 [Note] - '127.0.0.1' resolves to '127.0.0.1';
151208 8:13:08 [Note] Server socket created on IP: '127.0.0.1'.
151208 8:13:08 [ERROR] Fatal error: Can't open and lock privilege tables: Table 'mysql.host' doesn't exist
151208 08:13:08 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
151208 08:48:18 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
151208 8:48:18 [Warning] Using unique option prefix key_buffer instead of key_buffer_size is deprecated and will be removed in a future release. Please use the full name instead.
151208 8:48:18 [Note] /usr/sbin/mysqld (mysqld 5.5.46-0ubuntu0.14.04.2) starting as process 4808 ...
151208 8:48:18 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
151208 8:48:18 [Note] Plugin 'FEDERATED' is disabled.
/usr/sbin/mysqld: Table 'mysql.plugin' doesn't exist
151208 8:48:18 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
151208 8:48:18 InnoDB: The InnoDB memory heap is disabled
151208 8:48:18 InnoDB: Mutexes and rw_locks use GCC atomic builtins
151208 8:48:18 InnoDB: Compressed tables use zlib 1.2.8
151208 8:48:18 InnoDB: Using Linux native AIO
151208 8:48:18 InnoDB: Initializing buffer pool, size = 128.0M
151208 8:48:18 InnoDB: Completed initialization of buffer pool
151208 8:48:18 InnoDB: highest supported file format is Barracuda.
151208 8:48:18 InnoDB: Waiting for the background threads to start
151208 8:48:19 InnoDB: 5.5.46 started; log sequence number 763296054
151208 8:48:19 [Note] Server hostname (bind-address): '127.0.0.1'; port: 3306
151208 8:48:19 [Note] - '127.0.0.1' resolves to '127.0.0.1';
151208 8:48:19 [Note] Server socket created on IP: '127.0.0.1'.
151208 8:48:19 [ERROR] Fatal error: Can't open and lock privilege tables: Table 'mysql.host' doesn't exist
151208 08:48:19 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
151208 10:25:41 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
151208 10:25:41 [Warning] Using unique option prefix key_buffer instead of key_buffer_size is deprecated and will be removed in a future release. Please use the full name instead.
151208 10:25:41 [Note] /usr/sbin/mysqld (mysqld 5.5.46-0ubuntu0.14.04.2) starting as process 6652 ...
151208 10:25:42 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
151208 10:25:42 [Note] Plugin 'FEDERATED' is disabled.
/usr/sbin/mysqld: Table 'mysql.plugin' doesn't exist
151208 10:25:42 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
151208 10:25:42 InnoDB: The InnoDB memory heap is disabled
151208 10:25:42 InnoDB: Mutexes and rw_locks use GCC atomic builtins
151208 10:25:42 InnoDB: Compressed tables use zlib 1.2.8
151208 10:25:42 InnoDB: Using Linux native AIO
151208 10:25:42 InnoDB: Initializing buffer pool, size = 128.0M
151208 10:25:42 InnoDB: Completed initialization of buffer pool
151208 10:25:42 InnoDB: highest supported file format is Barracuda.
151208 10:25:43 InnoDB: Waiting for the background threads to start
151208 10:25:44 InnoDB: 5.5.46 started; log sequence number 763296054
151208 10:25:44 [Note] Server hostname (bind-address): '127.0.0.1'; port: 3306
151208 10:25:44 [Note] - '127.0.0.1' resolves to '127.0.0.1';
151208 10:25:44 [Note] Server socket created on IP: '127.0.0.1'.
151208 10:25:44 [ERROR] Fatal error: Can't open and lock privilege tables: Table 'mysql.host' doesn't exist
151208 10:25:44 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
151208 10:59:35 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
151208 10:59:35 [Note] Plugin 'FEDERATED' is disabled.
151208 10:59:35 InnoDB: The InnoDB memory heap is disabled
151208 10:59:35 InnoDB: Mutexes and rw_locks use GCC atomic builtins
151208 10:59:35 InnoDB: Compressed tables use zlib 1.2.8
151208 10:59:35 InnoDB: Using Linux native AIO
151208 10:59:35 InnoDB: Initializing buffer pool, size = 128.0M
151208 10:59:35 InnoDB: Completed initialization of buffer pool
151208 10:59:35 InnoDB: highest supported file format is Barracuda.
151208 10:59:37 InnoDB: Waiting for the background threads to start
151208 10:59:38 InnoDB: 5.5.46 started; log sequence number 763296054
151208 10:59:38 InnoDB: Starting shutdown...
151208 10:59:39 InnoDB: Shutdown completed; log sequence number 763296054
151208 10:59:39 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
151208 10:59:39 [Note] Plugin 'FEDERATED' is disabled.
151208 10:59:39 InnoDB: The InnoDB memory heap is disabled
151208 10:59:39 InnoDB: Mutexes and rw_locks use GCC atomic builtins
151208 10:59:39 InnoDB: Compressed tables use zlib 1.2.8
151208 10:59:39 InnoDB: Using Linux native AIO
151208 10:59:39 InnoDB: Initializing buffer pool, size = 128.0M
151208 10:59:39 InnoDB: Completed initialization of buffer pool
151208 10:59:39 InnoDB: highest supported file format is Barracuda.
151208 10:59:39 InnoDB: Waiting for the background threads to start
151208 10:59:40 InnoDB: 5.5.46 started; log sequence number 763296054
151208 10:59:40 InnoDB: Starting shutdown...
151208 10:59:41 InnoDB: Shutdown completed; log sequence number 763296054
151208 10:59:41 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
151208 10:59:41 [Note] Plugin 'FEDERATED' is disabled.
151208 10:59:41 InnoDB: The InnoDB memory heap is disabled
151208 10:59:41 InnoDB: Mutexes and rw_locks use GCC atomic builtins
151208 10:59:41 InnoDB: Compressed tables use zlib 1.2.8
151208 10:59:41 InnoDB: Using Linux native AIO
151208 10:59:41 InnoDB: Initializing buffer pool, size = 128.0M
151208 10:59:41 InnoDB: Completed initialization of buffer pool
151208 10:59:41 InnoDB: highest supported file format is Barracuda.
151208 10:59:41 InnoDB: Waiting for the background threads to start
151208 10:59:42 InnoDB: 5.5.46 started; log sequence number 763296054
ERROR: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'ALTER TABLE user ADD column Show_view_priv enum('N','Y') CHARACTER SET utf8 NOT ' at line 1
151208 10:59:42 [ERROR] Aborting
151208 10:59:42 InnoDB: Starting shutdown...
151208 10:59:43 InnoDB: Shutdown completed; log sequence number 763296054
151208 10:59:43 [Note] /usr/sbin/mysqld: Shutdown complete
151208 10:59:43 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
151208 10:59:43 [Note] Plugin 'FEDERATED' is disabled.
151208 10:59:43 InnoDB: The InnoDB memory heap is disabled
151208 10:59:43 InnoDB: Mutexes and rw_locks use GCC atomic builtins
151208 10:59:43 InnoDB: Compressed tables use zlib 1.2.8
151208 10:59:43 InnoDB: Using Linux native AIO
151208 10:59:43 InnoDB: Initializing buffer pool, size = 128.0M
151208 10:59:43 InnoDB: Completed initialization of buffer pool
151208 10:59:43 InnoDB: highest supported file format is Barracuda.
151208 10:59:43 InnoDB: Waiting for the background threads to start
151208 10:59:44 InnoDB: 5.5.46 started; log sequence number 763296054
151208 10:59:44 InnoDB: Starting shutdown...
151208 10:59:45 InnoDB: Shutdown completed; log sequence number 763296054
151208 10:59:45 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
151208 10:59:45 [Note] Plugin 'FEDERATED' is disabled.
151208 10:59:45 InnoDB: The InnoDB memory heap is disabled
151208 10:59:45 InnoDB: Mutexes and rw_locks use GCC atomic builtins
151208 10:59:45 InnoDB: Compressed tables use zlib 1.2.8
151208 10:59:45 InnoDB: Using Linux native AIO
151208 10:59:45 InnoDB: Initializing buffer pool, size = 128.0M
151208 10:59:45 InnoDB: Completed initialization of buffer pool
151208 10:59:45 InnoDB: highest supported file format is Barracuda.
151208 10:59:46 InnoDB: Waiting for the background threads to start
151208 10:59:47 InnoDB: 5.5.46 started; log sequence number 763296054
ERROR: 1050 Table 'plugin' already exists
151208 10:59:47 [ERROR] Aborting
151208 10:59:47 InnoDB: Starting shutdown...
151208 10:59:47 InnoDB: Shutdown completed; log sequence number 763296054
151208 10:59:47 [Note] /usr/sbin/mysqld: Shutdown complete
151208 10:59:48 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
151208 10:59:48 [Note] Plugin 'FEDERATED' is disabled.
151208 10:59:48 InnoDB: The InnoDB memory heap is disabled
151208 10:59:48 InnoDB: Mutexes and rw_locks use GCC atomic builtins
151208 10:59:48 InnoDB: Compressed tables use zlib 1.2.8
151208 10:59:48 InnoDB: Using Linux native AIO
151208 10:59:48 InnoDB: Initializing buffer pool, size = 128.0M
151208 10:59:48 InnoDB: Completed initialization of buffer pool
151208 10:59:48 InnoDB: highest supported file format is Barracuda.
151208 10:59:48 InnoDB: Waiting for the background threads to start
151208 10:59:49 InnoDB: 5.5.46 started; log sequence number 763296054
151208 10:59:49 [Note] Server hostname (bind-address): '127.0.0.1'; port: 3306
151208 10:59:49 [Note] - '127.0.0.1' resolves to '127.0.0.1';
151208 10:59:49 [Note] Server socket created on IP: '127.0.0.1'.
151208 10:59:49 [Note] Event Scheduler: Loaded 0 events
151208 10:59:49 [Note] /usr/sbin/mysqld: ready for connections.
Version: '5.5.46-0ubuntu0.14.04.2' socket: '/var/run/mysqld/mysqld.sock' port: 3306 (Ubuntu)
Ubuntu下mysql无法重启：http://www.linuxdiyf.com/linux/14787.html
Linux下查看MySQL的安装路径：http://www.linuxdiyf.com/linux/14760.html
ubuntu15.04手动安装MySQL5.6.27数据库：http://www.linuxdiyf.com/linux/14699.html
Ununtu 15.04安装MySql（Django连接Mysql）：http://www.linuxdiyf.com/linux/13783.html
Ubuntu15.04下MySQL5.6安装过程：http://www.linuxdiyf.com/linux/13250.html